The use of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET-СT) to determine the initial stage and assess the response to treatment for aggressive lymphomas is considered standard. Evaluation of bone marrow infiltration in PET-CT with 18F-FDG usually makes it possible to distinguish normal regenerating bone marrow after chemotherapy by the characteristic nature of absorption.

A 54-year-old patient diagnosed with diffuse large B-cell lymphoma (DLBCL) with lesions of the lymph nodes and bone marrow of the focal form with osteodestruction of the lytic type. Therapy at the A.F.Tsyba MRRC – 6 cycles of R-CHOP, completed in December 2022.

The PET-CT - 2 cycles is completely normalized. The February 2023, PET-CT showed an increase in the level of metabolism in one of the foci of osteodestruction in the pelvic bones. The biopsy, March 2023, absence of signs of DLBCL. PET-CT, June 2023, the increase of contrast accumulation in previously identified foci. Trepan biopsy in July 2023 – a picture of hematopoiesis foci in the bone marrow, a statement of remission. PET-CT scan in December 2023 confirming the remission of the disease.

False-positive PET-CT results in the era of rituximab began to be detected with greater frequency, therefore, their assessment and correct interpretation, as well as additional clarification using other available techniques, are necessary in modern clinical practice to choose tactics for further therapy.